The objective of the proposed research project is to study the processes of ventilation of the middle ear and sinuses. The purpose is to obtain knowledge that will have direct application to clinical diagnosis. An approved safe dosage of Xenon-133, a radioactive gas, will be administered to normal subjects by means of a negative-positive displacement technique that yeilds a given initial concentration of the gas in the sinus and middle ear cavities. The rate of egress of the gas from the different cavities will be measured using a scintillation camera that is interfaced to a PDP-15 computer. Simultaneously, two small probes (6mm diameter) will be placed at selected regions of interest and will collect data which will be printed out by portable clinical scalar counters. The computer data and the portable equipment data will be directly comparable so that the portable equipment can be assessed for its value as a diagnostic research tool. The normal subjects will be used twice: once to measure the rate of egress for a normal baseline, and then again to measure the effects of a variable on the rate of egress. Variables such as the influence of body position, repeated yawning, vaso constrictors, and warming of the tympanic membranes will be used during the research project. Subjects with confirmed pathology of the middle ear or sinuses will then be tested to determine if the desired correlation obtains in differential measures of normal and diseased patients.